Gas atmosphere generating means for heat-treating furnaces

ABSTRACT

Gas atmospheres for use in metallurgical furnaces are prepared by burning hydrocarbon gas and circulating the products of combustion, together with additional hydrocarbon gas, through a catalytic retort subjected to the heat produced by the combustion. The gas-generating apparatus has a valved outlet for withdrawing excess products of combustion to be used for purging furnaces. It also has valve-controlled auxiliary air and hydrocarbon gas inlets which can be adjusted to produce various gas compositions including AGA gas-types 101, 302 and 501.

United States Patent Crans [54] GAS ATMOSPHERE GENERATING MEANS FOR HEAT-TREATING FURNACES Roland C. Crans, Detroit, Mich.

Assignee: Holeroft & Company, Livonia, Mich. Filed: Sept. 15, 1969 Appl. No.: 858,030 g Inventor:

U.S. Cl ..23/28l, 252/376, 252/372, 48/ 190, 48/196 R, 263/15 R, 137/625.41

Int. Cl. ..Blj 7/00 Field ofSearch ..23/281; 252/372, 376; 263/15; 148/12, 16; 266/; 48/190, 180, 196, 197;

References Cited UNITED STATES PATENTS 9/1921 Niven ....l37/625.41X 6/1949 Hoop ..23/2s1 [451 Feb. 22, 1972 2,589,810 3/1952 Holcroft ..48/196 3,119,672 l/1964 Pierce ..48/190 UX FOREIGN PATENTS OR APPLICATIONS 681,614 /1952 Great Britain ..23/281 Primary Examiner-James H. Tayman, Jr. Attorney-Whittemore, l-lulbert & Belknap ABSTRACT Gas atmospheres for use in metallurgical furnaces are prepared by burning hydrocarbon gas and circulating the products of combustion, together with additional hydrocarbon gas, through a catalytic retort subjected to the heat produced by the combustion. The gas-generating apparatus has a valved outlet for withdrawing excess products of combustion to be used for purging furnaces. It also has valve-controlled auxiliary air and hydrocarbon gas inlets which can be adjusted to produce various gas compositions including AGA gas-types 101, 302 and 501.

7 Claims, 5 Drawing Figures FUR/1 05 R4 770 CONT/P04 VAZ l/E CONT/L m Will [S45 PATENTEDFEB22 I972 SHEET 1 OF 2 10* 5%; NKREQQ 5 gigs 6% S R Y WWW. M m PM W m km W ww fl g ud$$k E PATENTEDFEB-ZZ 1972 3,644, 099

SHEET 2 [IF 2 mhm INVENTOR ROAM 0 c CA AA/S wml MMV 5M ATTORNEYS GAS ATMOSPHERE GENERATING MEANS FOR I-IEAT- TREATING FURNACES BACKGROUND OF THE INVENTION 1960. Methods and apparatus for generating industrial gas atmospheres are disclosed in U.S. Pat. of Walter H. Holcroft Nos. 2,589,8 l0, and 2,589,8l I, both dated Mar. 18, 1952.

SUMMARY OF THE INVENTION The present invention relates to a gas generator capable of generating gases of various compositions. The new apparatus can be adjusted to operate either as an exothermic or an endothermic generator and, when desired, can simultaneously produce more than one type of gas. Typical of the compositions which can be produced are the following standard formulas of the American Gas Association:

AGA AGA AGA 101 501 302 N, 86.8 03.0 11 40.0 C 20.0 20.0 co, 10.11 11, 17.0 40.0 14,0 2.4

DRAWINGS FIG. 1 is a diagrammatic view of a gas generator.

FIGS. 2 and 3 show a portion of FIG. 1 with the valves in different positions of adjustment.

FIG. 4 is a diagrammatic view showing a modification control.

FIG. 5 is a diagram showing an arrangement for mixing the gases from the generator.

Referring to FIG. 1, it will be observed that the apparatus is similar in general outline to the I-Iolcroft converter illustrated in the publication by Bayer. It also can be operated in accordance with the disclosure in Holcroft U.S. Pat. No. 2,589,810. However, the new apparatus is structurally different from these prior art references and it has increased versatility and utility. For example, the new apparatus has means for adjustment whereby it can produce each of the AGA gases listed above and in some instances, it can simultaneously produce a plurality of such gases.

The new gas generator consists of a main casing 10 forming a combustion chamber 11, within which is a retort 12 containing catalytic material 13. A water tower 14 is connected by a conduit 15 to the outlet of the combustion chamber. Commercial combustible gas is drawn through gas inlet 16 by a pump 17 which also draws air through air inlet 18. Nineteen (19) is a ratio control valve by means of which the proportions of air and gas can be regulated. The combustible mixture of gas and air is delivered to a burner 20 discharging the products of combustion into chamber 11 and thereby supplying heat to the catalytic retort 12. The combustion gases are conducted through conduit 15 into water tower 14 where they are cooled to condense the water vapor formed during combustion. The gas is discharged from the water tower through outlet 21 and at this point consists mainly of nitrogen and carbon dioxide with a small amount of water vapor.

In accordance with U.S. Pat. No. 2,589,810, a part of the gas from the water tower may be combined with fresh hydrocarbon gas and fed into the catalytic retort 12. The hydrocarbon gas enters from the inlet 22. The two gases are combined in the conduit 23 in the desired proportions and are together circulated by pump 24 into the inlet 25 of retort 12.

Passing through the heated catalyst 13, the gas is reformed by chemical action into a gas composed mainly of carbon monoxide, hydrogen and nitrogen, and is then cooled in gas cooler 26 and discharged through conduit 27 to the metallurgical furnace. As thus far described, the apparatus follows the prior art practice. Also, it is usual to provide a branch conduit 28 leading from water tower outlet 21 to a vent 29 so that excess products of combustion not needed for the reforming action can be eliminated. The gas emerging from the water tower is of a composition suitable for use in certain metallurgical processes. One of the features of the present invention is to make available for possible use, any excess over that needed for the catalytic reforming instead of merely conducting all of such excess to the stack for waste gases. Accordingly, the generator of the present invention is provided with asecond branch conduit 30 near the water tower outlet 21 so that gas not needed to pass through the main conduit 31 by action of pump 24, can be passed through control valve 32 to a gas supply port 33. Thus only the excess gas not used either for catalytic reforming or for direct useful work will be wasted through vent 29. This second branch conduit 30 has other functions also as will be hereinafter pointed out.

The main conduit 31 for the combustion products from water tower outlet 21 has a main channel 34 leading to mixture conduit 23. There is also a bypass channel 35, the latter being provided with a ratio control valve 36. Similarly the hydrocarbon gas line from gas inlet 22 has a main channel 37 leading to mixture conduit 23. There is also a bypass channel 38 in parallel with the main channel. At the junction of channels 34, 37 and 23, a three-port, two-way valve 39 is located. In the bypass 38 there is an orifice 38A and there is also a shutoff valve 40. In the channel 37 there is another shutoff valve 41. At the point where the three-port valve 39 is located, there is a conduit 42 having a main channel 43 leading to an air inlet orifice 44. A bypass channel 45 in parallel with the main channel 43 is provided with a ratio control valve 46. The hereinbefore described valves 39, 40 and 46 together with the associated channels 39, 42, 43 and 45 are all new and form no part of the prior art generators. The addition of these new parts and their association in a novel manner with the other elements of the gas generator hereinbefore described produces the improved apparatus of the present invention. By a simple manipulation of the valves, the new gas generator can be quickly adjusted to produce a plurality of different gas compositions useful in connection with metallurgical furnaees.

In FIG. 1 the valves are shown so that the generator operates in accordance with U.S. Pat. No. 2,589,810. It will be observed that valve 41 is open, valve 40 is closed and valve 39 interconnects channels 34, 37 and 23. With this arrangement, the products of combustion from water tower outlet 21 proceed through conduits 31 and 34 through valve 39 into conduit 23. Hydrocarbon gas from inlet 22 proceeds through open valve 41, conduit 37 and valve 39 into conduit 23. The controlled mixture of these two gases enters the catalytic retort 12 where the mixture is reformed by chemical action and then conducted by conduit 27 to the metallurgical furnace. The gas produced by this process is known as AGA 50] and contains 20 percent carbon monoxide, 17 percent hydrogen and the balance nitrogen. In ordinary usage of a gas generator with the valves as shown in FIG. 1, there is usually an excess of products of combustion at water tower outlet 21. This excess can be utilized for any desired purpose by opening valve 32. Any unused amount of combustion products will escape through vent 29 in accordance with standard practice.

FIG. 2 shows the valves adjusted so that valve 41 is closed and valves 39 and 40 remain as in FIG. 1. With this arrangement only the products of combustion are circulated through the catalytic retort because the hydrocarbon gas supply is shut off by the closed valve 41. The gas emerging from conduit 27 and delivered to the metallurgical furnace is known as AGA 101. While such gas may not be suitable for many metallurgical processes, it is useful for purging air from a furnace so that later addition of a combustible gas does not present any hazard. Thus any new generator may be connected to such a furnace and operated with the valves as in FIG. 2 for a certain length of time to purge the furnace with noncombustible gas issuing from conduit 27. At the same time, any excess of noncombustible gas can be utilized for other purposes by reason of its availability from gas supply port 33. When the furnace is sufficiently purged, valve 41 can be opened, thus restoring the valves to the condition shown in FIG. 1, whereupon the generator will commence to produce the reducing gas of formula AGA 501 as hereinbefore described in connection with the operation of FIG. 1.

FIG. 3 shows the valves in another position of adjustment. Two-way valve 39 now shuts off conduit 23 from channel 34 and connects 23 to the air supply from air inlet 44 and also connects 23 to the hydrocarbon gas supply from inlet 22. Since bypass valve 40 is also open, this permits additional hydrocarbon gas to pass through the bypass 38 thus increasing the amount of hydrocarbon relative to the air supply. The proper ratio determined by means of the orifice 38A will produce a gas known as AGA 302 higher in hydrogen content than AGA 501. At the same time, combustion products (Type 101) are available at supply port 33 because gas must still be burned at burner to produce the heat for catalytic reforming, even through the combustion products themselves are not needed in the retort 12 when 501 gas is being produced. The combustion products are excluded from retort 12 because, in FIG. 3, valve 39 shuts off the supply from 34 to 23.

It will be noted that valves 39 and 40 are always in the same position relative to each other in each of the arrangements shown in FIGS. 1, 2, and 3. Hence, it is another feature of this invention to mechanically interlock valves 39 and 40, as diagrammatically indicated at 50, so that they are simultaneously moved to maintain the proper relationship to each other.

In the operation of the apparatus herein described, it is necessary to proportion the amounts of air and fuel as is well understood in the art. These proportions are controlled by the use of calibrated orifices and ratio control valves as illustrated in the drawings. For the conditions shown in FIG. 1, the combination of the orifices used in the combustion products lines 34 and 35 and in the hydrocarbon gas lines 37 and 38 is preferably such that the mixture drawn by pump 24 through the line 23 and introduced into the catalytic retort is 7.53 parts of combustion products to 1 part of hydrocarbon gas. This will produce in the catalytic reformer a 501-type gas.

For the conditions shown in FIG. 3, the combination of the orifices in the air line 42 and the hydrocarbon gas line 37 is such that the resulting mixture is 2.5 parts of air to 1 part of hydrocarbon fuel. This will produce in the discharge line 27 a 302-type gas.

For the condition shown in FIG. 2, the gas produced in the discharge line 27 is the same as that from the water tower outlet 21 and is an exothermic, noncombustible gas of Type 101.

The apparatus as hereinbefore described has multiple capabilities depending upon the manipulative adjustment of the various valves including the following:

1. To produce only Type 101 noncombustible gas for use in processing or for purging air or combustible gas from a furnace.

2. To produce Type 501 gas at one outlet and simultaneously produce Type 10] gas at another outlet.

3. To produce Type 302 gas at one outlet and simultaneously produce Type 101 gas at another outlet.

Instead of using the three-port, two-way valve 39, a modified valve arrangement can be used as shown in FIG. 4. The three conduits 34, 37 and 42 for combustion products, hydrocarbon gas, and air, respectively, are connected to the mixed gas outlet conduit 23 and individual valves 51, 52 and 53 are located in the respective conduits. Other suitable valving means can also be used in place of the interconnected valves 39 and 40. in the apparatus, as previously described, it has been pointed out that the gas supply port 33 serves to distribute Type 101 combustion gas while conduit 27 supplies either Type 302 or Type 501 depending on the valve adjustment. It is common practice with gas generators to distribute gas to more than one furnace or to more than one area in a single furnace through distribution orifices in the pipelines.

FIG. 5 illustrates an arrangement whereby the various gases may be blended in such a way as to produce a variety of resulting combustions for furnaces. Thus the outlet port 33 is connected to a pipeline 5 while conduit 27 is connected to pipeline 55. The conduit 54 has branch pipes 56, 57 and 58, each controlled by a valve 59, 60 and 61 together with orifices 62, 63, and 64. correspondingly, the pipe 55 has branch conduits 66, 67, and 68 with control valves 69, 70 and 71 as well as orifices 72, 73 and 74. The respective branch conduits are provided with furnace outlets 75, 76 and 77. With this arrangement, by providing the proper calibrated orifices, the blends of gases to individual furnaces can be varied infinitely from Pure 302 or Pure 501 to Pure 101 or any intermediate composition.

What I claim as my invention is:

1. Gas atmosphere generating means for heat-treating furnaces comprising a combustion chamber, a retort in heat-conducting relation to said combustion chamber, means for introducing into said chamber a combustible mixture of gaseous fuel and air to be burned in said chamber thereby heating said retort, means for passing the products of combustion through a water tower to condense out most of the water, a first conduit for the condensed combustion products leading from the outlet of said water tower, a second hydrocarbon gas supply conduit, a third air supply conduit, a fourth mixing conduit leading from the aforesaid three conduits to said retort, a valve means controlling said conduits, a catalyst in said retort capable of reforming the gases therein, a discharge conduit from said catalytic retort, a branch conduit extending from said water tower outlet to an atmospheric vent and a second valve-controlled utility branch conduit connected to said water tower outlet for utilizing excess combustion products not circulated through said retort.

2. Apparatus according to claim 1 wherein said four conduits for combustion products, hydrocarbon gas supply, air supply, and the mixture from the same are all connected together by means of a three-port, two-way valve, having two positions of adjustment, one connecting together said first, second and fourth conduits while disconnecting said third conduit, and the other position disconnecting said first conduit while connecting together said second, third and fourth conduits.

3. Apparatus according to claim 2 in which there is a hydrocarbon gas valve in said second hydrocarbon gas supply conduit which can be alternatively opened or closed when said three-port valve is in either of said adjusted positions, thereby selectively supplying hydrocarbon gas to said fourth mixture conduit.

4. Apparatus according to claim 3 in which there is a valvecontrolled bypass in said second hydrocarbon supply, conduit, and said bypass valve is interconnected to said three-port valve.

5. Apparatus according to claim 4 wherein said three-port and bypass valves are interconnected to operate in unison.

6. Apparatus according to claim 1 in which said discharge conduit from said catalytic retort and said utility branch conduit for combustion gases are connected together by a series of interconnecting conduits, each having an outlet for the mixed gases from catalytic retort and combustion gas respectively and a series of regulating devices for proportioning said respective catalytic and combustion gases.

7. Apparatus according to claim 5 in which said discharge conduit from said catalytic retort and said utility branch conduit for combustion gases are connected together by a series of interconnecting conduits, each having an outlet for the mixed gases from catalytic retort and combustion gas respectively and a series of regulating devices for proportioning said respective catalytic and combustion gases. 

2. Apparatus according to claim 1 wherein said four conduits for combustion products, hydrocarbon gas supply, air supply, and the mixture from thE same are all connected together by means of a three-port, two-way valve, having two positions of adjustment, one connecting together said first, second and fourth conduits while disconnecting said third conduit, and the other position disconnecting said first conduit while connecting together said second, third and fourth conduits.
 3. Apparatus according to claim 2 in which there is a hydrocarbon gas valve in said second hydrocarbon gas supply conduit which can be alternatively opened or closed when said three-port valve is in either of said adjusted positions, thereby selectively supplying hydrocarbon gas to said fourth mixture conduit.
 4. Apparatus according to claim 3 in which there is a valve-controlled bypass in said second hydrocarbon supply, conduit, and said bypass valve is interconnected to said three-port valve.
 5. Apparatus according to claim 4 wherein said three-port and bypass valves are interconnected to operate in unison.
 6. Apparatus according to claim 1 in which said discharge conduit from said catalytic retort and said utility branch conduit for combustion gases are connected together by a series of interconnecting conduits, each having an outlet for the mixed gases from catalytic retort and combustion gas respectively and a series of regulating devices for proportioning said respective catalytic and combustion gases.
 7. Apparatus according to claim 5 in which said discharge conduit from said catalytic retort and said utility branch conduit for combustion gases are connected together by a series of interconnecting conduits, each having an outlet for the mixed gases from catalytic retort and combustion gas respectively and a series of regulating devices for proportioning said respective catalytic and combustion gases. 